Abstract: An air or gas sprung and dampened shock absorber for a bicycle is set forth comprising a cylinder having a closed end and an open end forming a compression chamber, a shaft having a closed end and an open end, the open end of the shaft being reciprocally received within the cylinder through the open end of the cylinder, a piston sealingly positioned in the open end of the shaft and slidably and sealingly positioned adjacent an inner surface of the cylinder forming a rebound chamber in the shaft and a gas spring chamber formed between an outer surface of the shaft and an inner surface of the cylinder wherein the gas spring chamber communicates with the rebound chamber during at least a portion of the compression and rebound stroke of the shock absorber. The shock absorber further includes a compression plate sealingly received in the shaft with an axial position of the compression plate being selectively moveable within the shaft for varying a total volume of the shock absorber.